A vehicle headlamp (also referred to as a headlamp or a headlight) generally includes a high beam (running headlamp) and a low beam (passing headlamp) (for example, PTL 1). The high beam can irradiate a wide range of a front of a vehicle, but give dazzle to a driver of an oncoming vehicle. The low beam does not give dazzle to the driver of the oncoming vehicle, but there is a problem that the low beam cannot irradiate a wide range of the front of the vehicle.
In recent years, a system, in which a presence or position of the oncoming vehicle or a preceding vehicle is detected by a camera placed on a vehicle, and the light of the vehicle headlamp giving dazzle to the driver of the vehicle is shielded, has been developed. Such a system is generally referred to as an adaptive driving beam (ADB) system.
For example, as illustrated in FIG. 13, high beam SW of the vehicle headlamp of the related art using the ADB system includes a plurality of LED light source modules M1 to M4 as light emitting elements and a plurality of lenses S1 to S4 for emitting the lights generated from LED light source modules M1 to M4 in a desired direction. Focal points of lenses S1 to S4 are generally positioned on light emitting surfaces of LED light source modules M1 to M4. Therefore, the lights generated from LED light source modules M1 to M4 become parallel lights through lenses S1 to S4. In addition, LED light source modules M1 to M4 of high beam SW are automatically switched on and off respectively when the camera detects the presence of the oncoming vehicle or the preceding vehicle. In this way, an irradiation range of high beam SW of the vehicle headlamp is controlled.
In a case where the lights emitted from lenses S1 to S4 are the parallel lights, light and dark between the irradiation range and a portion that is not in the irradiation range is clearly distinguished. Here, a positional deviation of light distribution characteristics of lenses S1 to S4 occurs due to vibration or temperature changes of lenses S1 to S4, assembly errors of the vehicle headlamp, or the like. The light distribution characteristics of the lens indicate a relationship between a direction of the light emitted from the lens and a luminous intensity distribution in the direction. Light distribution unevenness occurs due to the positional deviation of the light distribution characteristics.